We intend to synthesize oligoribonucleotides and RNA with a 2 feet -SH substitution. As starting material for the chemical process, we need the thio analog of natural 2 feet :3 feet -CMP which will be polymerized via transesterification. Diphosphates of 2 feet -thionucleosides will also be obtained and polymerized by the action of polynucleotide phosphorylase. Micelles will be used as catalytic medium for oligonucleotide synthesis. Chemical and physico-chemical studies will be carried out on di- and trinucleotide analogs which are expected to behave structurally similar to the natural nucleotides but should possess greater stability to hydrolysis. The action of all nucleases will be observed on the new analogs. Among expected biological activities, the potential to induce interferon by double stranded complexes is the most outstanding. Possible cytotoxic effect on mammalian cells will be observed. It is hoped that the existence of 2 feet-SH-RNA will extend our outstanding of the various RNA species and functions while also providing potential drugs.